1. Field of the Invention
The invention relates to projection displays, more particularly to a projection display having a twin-blower heat-dissipating system.
2. Description of the Related Art
It is a growing trend in the industry to reduce the size of projection displays for the purpose of portability. However, aside from portability, heat-dissipation and noise-reduction are also important factors that have to be taken into consideration in the design of projection displays.
Referring to FIGS. 1 and 2, a conventional liquid crystal projection display 1 is shown to comprise a light source 11 contained in a housing (not shown). White light radiated by the light source 11 is processed by a number of optical elements, such as filters, integrators, polarized beam splitting prisms, beam splitters, mirrors, etc., so as to separate the same into different color components, e.g. red, blue and green color components, that are directed respectively to three light modulators 12, 13, 14 for light modulation. The modulated color components are subsequently combined with the use of a color recombination unit 15, and are eventually projected with the use of a projection lens 16. The light modulators 12, 13, 14 are generally disposed respectively adjacent to right lateral, left lateral and rear sides of the recombination unit 15.
It is noted that heat is generated at the vicinity of the light modulators 12, 13, 14 during operation of the projection display. The generated heat must be dissipated to prevent image degradation and breakdown of the projection display.
FIG. 2 illustrates a conventional arrangement for dissipating heat in the projection display 1. As shown, a fan 17 is disposed beneath the light modulators 12, 13, 14 and the recombination unit 15, and generates upwardly directed cooling air currents. Of course, it is also possible to install the fan 17 above the light modulators 12, 13, 14 and the recombination unit 15. In the latter case, the fan 17 generates downwardly directed cooling air currents.
Some of the drawbacks of the conventional heat-dissipating arrangement of FIG. 2 are as follows:
1. The location of the fan 17 necessitates an increase in the thickness of the projection display 1. In addition, adequate clearances must be present at the air inlet and air outlet for efficient heat dissipation.
2. A dust cover (not shown) is usually disposed at the air inlet to protect the fan 17. If the fan 17 is not adequately spaced apart from the dust cover, a large air resistance and a relatively loud noise are generated. If the fan 17 is spaced far apart from the dust cover, a further increase in the thickness of the projection display 1 is incurred.
3. Because the air currents generated by the fan 17 only flow directly upward or downward, they cannot be relied upon to cool other parts of the projection display 1.
FIG. 3 illustrates another conventional liquid crystal projection display 2 with a single-blower heat-dissipation system. As shown, a blower unit 22 is disposed at one side of a projection lens 21. The blower unit 22 draws cooling air in a first direction, and releases the cooling air in a second direction that is transverse to the first direction. The cooling air from the blower unit 22 moves along the light modulators 23, 24, 25 for cooling the latter. While the heat-dissipating arrangement of FIG. 3 does not incur a considerable increase in the thickness of the projection display 2, it is noted that the cooling air from the blower 22 is only used to cool the vicinities of the light modulators 23, 24, 25. In addition, because a blower unit is generally characterized with a higher airflow resistance as compared to a similarly sized fan, the blower unit usually has a lower airflow rate than a fan of the same size. Thus, a single blower unit is insufficient to achieve effective heat dissipation in a projection display with a high brightness design. While it is possible to increase the blower speed to increase the airflow rate, this will involve a corresponding increase in noise.
FIG. 4 illustrates yet another conventional liquid crystal projection display 3 with a triple-blower heat-dissipation system. As shown, a first blower unit 321 is disposed at one side of a projection lens 31, whereas second and third blower units 322, 323 are disposed at the other side of the projection lens 31. Each of the blower units 321, 322, 323 draws cooling air from the outside, and provides the cooling air to a respective one of three light modulators 331, 332, 333 for cooling the latter. While the heat-dissipating arrangement of FIG. 4 does not incur a considerable increase in the thickness of the projection display 3, and is capable of providing adequate air currents for efficient cooling, the use of the three blower units 321, 322, 323 involves a large increase in both manufacturing cost and noise, and necessitates a large installation space for the blower units 321, 322, 323. There is thus a need to reduce the size of other components, such as circuit boards, inside the projection display 3 to compensate for the increase in the volume attributed to the blower units 321, 322, 323. Moreover, the cooling air currents from the blower units 321, 322, 323 are only used to cool the vicinities of the light modulators 331, 332, 333.
Therefore, the main object of the present invention is to provide a projection display having a twin-blower heat-dissipating system that is capable of overcoming the aforesaid drawbacks of the prior art.
According to this invention, a projection display comprises a color recombination unit, a projection lens, first and second light modulators, and first and second blower units. The color recombination unit has a front side, a rear side opposite to the front side, and opposite first and second lateral sides that extend between the front and rear sides. The projection lens is disposed adjacent to the front side of the color recombination unit, and has opposite first and second sides. The first light modulator is disposed adjacent to one of the first and second lateral sides and the rear side of the color recombination unit. The second light modulator is disposed adjacent to another one of the first and second lateral sides and the rear side of the color recombination unit. The first and second blower units are respectively disposed adjacent to the first and second sides of the projection lens. The first blower unit has a first air inlet, a first air outlet with an axis transverse to that of the first air inlet, and a first air passage that fluidly communicates the first air inlet and a vicinity of the first light modulator. The first blower unit is operable such that air from the vicinity of the first light modulator can be drawn into the first air inlet via the first air passage, and can be subsequently released via the first air outlet. The second blower unit has a second air inlet, a second air outlet with an axis transverse to that of the second air inlet, and a second air passage that fluidly communicates the second air inlet and a vicinity of the second light modulator. The second blower unit is operable such that air from the vicinity of the second light modulator can be drawn into the second air inlet via the second air passage, and can be subsequently released via the second air outlet.